Process of bleaching cotton



users crass arr oas P P. DASBET'I, OF OYNTEIANA, m'rucxr.

EBOOEBS OI BLEAOEING COTTON- F 1,402,040. Swill-Mien 01 mm! e Patented Jan. 3, 1922. an Drawing. Application filed April 19, mo." Serial No. man.

To all whom it may concern:

Be it known that I, Hnanr P. Bsssm'r, a citizen of the United States residing at Cynthiana in the county of l-Iarrison and State of entucky, have invented certain new and useful Improvements in Processes of Bleaching Cotton, of which the following is a specification.

This invention relates to processes of bleaching cotton and comprises a method of treating cotton fiber wherein the material is treated with a weak acid solution of a. definite predetermined strength to hydrolyze the tgummy constituents resent as impurities in e raw material, was ing the material to remove any soluble bodies formed in the h drolysis, treating with a weak solution of afkali of a definite predetermined stren h to form salts of the organic acids forme in the h drol washing to remove the salts and t on iiting wit a bleaching agent' all as more fully hereinafter set forth an as claimed.

In the production of fibrous material from cotton, it is customary to treat the raw material with a strong solution of an alkali to hydrolyze the typical waxes and gums pres cut as impurities, and which must be removed to produce a d fiber. I have found that this method oes not com letely remove the impurities from the her. The hydrolysis with a strong alkaline solution does not produce entirely soluble salts which may be readily removed from the fiber by washin It has therefore, been necessary to. crap oy a re tively large amount of bleaching material to bleach the im urities resent which are not removed by t e bylysis. A. further disadvanta of this method resides in the fact that t e impurities are present in the finished materi and the fiber is inferior in quality.

A further disadvantage of the present methods of treatin cotton fibers resides in the fact that there is a tendency of the alkali and the bleaching material to react upon the cellulose, changing the chemical composition and forming oxy-cellulose and similar bodies. This injures the fibrous structure and makes it unsuitable for many uses, such as, for instance, the manufacture of nitro-cellulose and cellulose acetate, etc.

In the present process, I have found that a much better material may be produced at a relatively lower cost if the material is first hydrolyzed with a weak acid solution of a proximately one r cent strength by weig t. or less. After t e h drolysis, the material is treated witha w solution of an alkali of approximately one per cent strength by weight, or loss, which forms salts of the organic acids with the hydrolized waxes and resins present in the raw material. This treatment with the weak acid solution and the weak solution of an alkali removes all impurities from the cotton fiber the salts of the or nic acids roduccd by the alkali bemg so uble and sing washed out in the treatment, and being further washed with water to entirely remove the salts.' The fibrous material is then ready for the bleachmg step and a relatively small amount of the bleach ma be used and a finished material obtain free from any coloring or im urities.

be weak alkaline solution used and the relatively small amount of bleach employed removes the possibility ofreaction y the alkaline solution or the bleach and the cellulose bodies present in the cotton fiber and thus eliminates the possibilit} of forming oxy-cellulose and similar bodies, which are detrimental in many uses in which the finished cellulose is employed.

As stated, when the hydrolysis is performed with an alkali, the compounds produced are not all freely soluble in water and the result is that some of the impurities are not removed by the subsequent washi step. Under such conditions, it is necessary i emplo a. large amount of bleaching material an this isa dlsadvanta as the bleaching material itself has a ten ency to least u n the cellulose bodies of thefiberfiand re use city-cellulose and similar bodies. 11 addition, it has been found impossible to completely remove all color from some fibrous materials by the bleaching operation, even when a very strong bleaching solution is empliiyed.

n the dpresent process, the cotton fiber is so treats that the original structure is not injuriously aflected and the chemical comosition of the cellulose bodies is unchanged, but practically all impurities are removed. When the material is submitted to the bleaching step, only a very small amount of bleach is necessary to remove all color from the fibrous material and produce a practically pure cellulose fiber.

In the present invention, the raw cotton fibers are first treated with the weak acid solution. An acid which is capable of furnishing a hy gen ion in the hydrolysis of the typical waxes and resins present as impurities in the raw material may be emloyed. For commercial purposes, I have ound that the mineral acids, such as sulfuric acid and hydrochloric acid are best adapted for the performance of the process, but the invention is in no way limited to the use of either of these acids, or to the use of a mineral acid. The relative cheapness of the mineral acids such as sulfuric acid and hydrochloric acid and their greater eliiciency in furnishin the hydroggn ion for hydrolysis makes t em prefers, le in the practice of the process from a commercial standpoint.

The acid treatment removes the sugar originally present in the typical waxes and resins, and may wash out some of the more soluble organic acids formed by hydrolysis. The material is then submit to washing to remove any other soluble bodies present before treatment with the alkali. It is then treated with a weak solution of an alkali, such as any basic compound of an alkali or alkaline earth metal which will combine with the organic acids to form soluble salts of the organic acids. I have found that sodium and potassium com ounds, such as sodium or potassium car onate, caustic soda, or caustic potash, are well suited for this operation, but the invention is not limited to the use of any of the materals mentioned.

After the treatment with the alkali, the impurities present are all in the form of soluble salts of the organic acids and they may be readily removed by washing. This 0 oration is best performed with hot water, t e material being washed in any of the usual methods until all, or practically all, of the impurities are removed. The matcrial is then ready for the bleaching operation, and the-cellulose bodies forming the fiber are present in a chemically unchanged -oondition due to the relative weakness of the acid and alkaline solutions used, but in a physical condition particularly adapted to respond readily to the action of the bleachin agent. The impurities are iractically al removed by the treatment wit the acid and alkaline solutions and the subsequent washing steps, and a very small amount of a bleaching agent may be used. Any of the well known bleaching agents may be employed and I have obtained a practicall White fiber by bleaching the material in the usual manner with a solution of calcium hypochlorite, containing a fraction of one or cent of the bleaching agent.

While I refer to employ solutions of acid and alkali of one per cent strength or less, I have found that satisfactory results may be obtained by employing solutions of from five-tenths to one and one-half per cent strength. In the case of the acid, I have obtained commercially satisfactory results by using a strength of one-fourth of one per cent, and in the case of the solution of alkali, I .have obtained commercially satisfactory results from the use of a solution having a strength as high as two and one-half per cant I I am aware that a weak solution of acid has been used to hydrolyze typical waxes and loosen the fiber of flax, straw, and the like from the shire, and that a weak solution of acid has been used to loosen or separate the fiber of flax and like material from the shive, and that the combined use of both steps has been roposed, as set forth in Letters Patent 0. 1,046,536, granted to me December 16, 1912.

It is, however, well understood by chemists familiar with flax and like stalks, that their physical composition is rugged and that their chemica make-up differs substantially from that of cotton, particularly in respect of the binding agents of the fibers.

I am also aware that it has been pro used to treat cotton fibers with a weak soution of an alkali followed by a weak solution of an acid, but the advantages of the present process cannot be obtained by such treatment; nor by treatin cotton fibers with a strong acid solution ollowed by the use of either a weak or a strong solution of an alkali; nor by the treatment with a strong acid solution after a preliminary treatment wlth'a weak acid solution.

Having thus described my invention, I claim:

1. The process of bleaching cotton fibers which comprises hydrolyzing the t ical gums and resins present in the fibers with an acid solution of not in excess of substaiitially one and one-half per cent stren to form soluble sugars and organic acids, washing to remove the sugars and the Soluble organic acids, treatin with an alkaline solution of not in excess o substantially two and one-half per cent strength to form salts of the organic acids, washing to remove the salts formed, and bleaching.

2. The process of bleaching cotton fibers which comprises hydrolyzing the typical gums and resins present in the fibers with a solution of mineral acid of substantially less than one per cent stren h, washing to remove the sugars and t e soluble organic acids, treating with an alkaline solution of not in excess of approximately two and onehall per cent stren h, to form salts of the organic acids, was ing to remove the salts formed, and bleaching.

3. The process of bleaching cotton fibers which comprises hydrolyzing the typical gums and resins present in the fibers with an substantially acid solution of not in excess of substantially one per cent strength, washing to remove the sugars and the soluble organic salts, treat with an alkaline solution of not in excess 0 one per cent strength to form salts of the or anic acids, washing to remove the salts i ormed and bleaching. 4. The process of bleaching cotton fibers which comprises hydrolyzin the typical gums and'resins present in t e fibers with an acid solution of substantially less than one per cent strength, washing to remove the sugars and the so uble orgamc acids, treating with an alkaline solution of not in excess of one per cent strength to form salts of the organic acids, washing to remove the salts formed, and bleaching.

5. The process of bleaching cotton fibers which comprises hydrolyzing the typical gums and resins present in the fibers with a solution of sulfuric acid of not in excess of approximately one per cent strength, washing to remove the sugars and the soluble organic acids, treating with a solution of cans tic soda of not in exceess of approximately per cent strengthi washing to remove the sugars and the so uble organic acids, treating with a solution of caustic soda of not in 86 excess of one per cent strength to form salts of the organic acids, washing to remove the salts formed, and bleaching.

In testimon whereof I aifix my signature in presence 0 a witness.

HARRY P. BASSETT.

Witness Man! F. Lyons.

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